The present invention relates to a gas flow rate measuring apparatus useful for measuring the flow rate of the intake air for the engine or an like.
In a of fuel injection type engine, the intake air flow rate is measured and the fuel commensurate with the measured amount of air is supplied by injection into the engine. A well known intake air flow rate measuring apparatus of this type used for the engine comprises a flow rate measuring tube in the intake manifold of the engine, a platinum resistance wire for an electric heater disposed in the tube, a pair of platinum temperature dependent resistance wires also disposed within the tube, and means for measuring the flow rate of the intake air (gas to be measured) in response to an output signal from the resistance wires. This conventional apparatus essentially has an advantage that the flow rate of the gas can be measured accurately with a compact and simple construction.
In this device, it is effective to hold the resistance wires in the measuring tube by winding the wires on a support made of an insulating material. By doing so, each resistance wire is prevented from breaking due to vibrations or backfire of the engine.
If the resistance wires are wound on the support in simple manner, however, the relative position of the resistance wires with the support are varied on the one hand and the resistance wires may be displaced by the wind pressure caused by the backfire on the other hand. The displacement of these resistance wires very undesirably deteriorates the accuracy of flow rate measuring.